Depth of sedation using the RASS. The target RASS range (target depth of sedation) should be 0 to -3 for a patient to be included in the study. The target may be amended during the study treatment, if clinically required [ Time Frame: RASS score will be assessed approximately 2 hourly during the treatment period and during the 48-hour follow-up period ] [ Designated as safety issue: Yes ]

Duration of mechanical ventilation the number of days the patient receives mechanical ventilation will be recorded [ Time Frame: This variable will be dependent on the individual patient and the number of days they require mechanical ventilation . ] [ Designated as safety issue: No ]

Original Primary Outcome Measures ICMJE (submitted: May 31, 2007)

Depth of sedation using the RASS. The target RASS range (target depth of sedation) should be 0 to -3 for a patient to be included in the study. The target may be amended during the study treatment, if clinically required [ Time Frame: RASS score will be assessed approximately 2 hourly during the treatment period and during the 48-hour follow-up period ]

Duration of mechanical ventilation the number of days the patient receives mechanical ventilation will be recorded [ Time Frame: This variable will be dependent on the individual patient and the number of days they require mechanical ventilation . ]

Nurse's assessment of subject communication with visual analogue scales (VAS)Patients rousability and ability to co-operate and communicate will be measured using a visual analogue scale. [ Time Frame: This will be measured at the end of every nursing shift whilst the patient remains on study treatment (maximum 14 days) ] [ Designated as safety issue: Yes ]

Length of ICU stay [ Time Frame: Number of days a patient is in ICU which will vary depending on the underlying illness of the patient ] [ Designated as safety issue: No ]

Original Secondary Outcome Measures ICMJE (submitted: May 31, 2007)

Nurse’s assessment of subject communication with visual analogue scales (VAS)Patients rousability and ability to co-operate and communicate will be measured using a visual analogue scale. [ Time Frame: This will be measured at the end of every nursing shift whilst the patient remains on study treatment (maximum 14 days) ]

Length of ICU stay [ Time Frame: Number of days a patient is in ICU which will vary depending on the underlying illness of the patient ]

Patients in ICU who need help with their breathing are put onto a machine called a ventilator and are also given a medicine, called a sedative, which helps them to sleep and makes them more comfortable. Midazolam is a sedative that is routinely used for these purposes.

For most patients the aim of sedation is to make them sleepy but still able to respond to nursing staff (light sedation)

Dexmedetomidine is a new sedative for use in intensive care and in this clinical study, dexmedetomidine is compared to midazolam. It is thought that dexmedetomidine might be slightly better at allowing patients to be sleepy but still respond to people around them. It also does not appear to affect patient's breathing. the purpose of this study is to test whether dexmedetomidine really does have these advantages compared to midazolam.

in this study we hope to show that: dexmedetomidine is at least as good as midazolam in helping patients to sleep better and making them more comfortable, and that they are able to co-operate better with the staff treating them, and that patients treated with dexmedetomidine require a shorter time on the ventilator than those treated with midazolam.

All patients admitted to ICU will be pre-screened according to inclusion and exclusion criteria prior to informed consent using available clinical data.

Informed consent, screening and randomisation procedures should be completed within 72 hours from the time of admission to ICU and within 48 hours from starting continuous sedation. Eligible study subjects requiring light to moderate sedation (Richmond Agitation-Sedation Scale [RASS] = 0 to -3) will be randomised to either continue on midazolam or switch to dexmedetomidine. Patients should not have received any other continuously or regularly administered sedative agent than midazolam infusion during the last 12 hours except for opioid analgesics. Study treatments will be titrated to achieve an individually targeted sedation range determined on a daily basis. Rescue treatment (i.e. propofol boli) may be given if needed to achieve the target depth of sedation. Continued need for sedation will be assessed at a daily sedation stop, conducted at the same time each day. First sedation stop may be 12-36 hours from randomisation, depending on the time of day the study subject is randomised. The duration of study treatment is limited to a maximum of 14 days from randomisation. Following withdrawal of sedation, study subjects will be monitored for 48 hours and contacted by telephone 31 and 45 days after randomisation.

Patients who are unlikely to be weaned from mechanical ventilation; e.g. diseases/injuries primarily affecting the neuromuscular function of the respiratory apparatus such as clearly irreversible disease requiring prolonged ventilatory support (e.g. high spinal cord injury or advanced amyotrophic lateral sclerosis)

Distal paraplegia

Positive pregnancy test or currently lactating

Received any investigational drug within the preceding 30 days

Concurrent participation in any other interventional study (any study in which patients are allocated to different treatment groups and/or non-routine diagnostic or monitoring procedures are performed)

Previous participation in this study

Any other condition which, in the investigator's opinion, would make it detrimental for the subject to participate in the study

Gender

Both

Ages

18 Years and older

Accepts Healthy Volunteers

No

Contacts ICMJE

Contact information is only displayed when the study is recruiting subjects